Bob,
I have been working on a fail safe system for some time now, and I have been flying it in one of my demo Super Hornets. This system is all electronic programable, and T's into the air system. The unit is pre-set to your desired minimum air pressure level, and hooked into your retract servo line. When the air pressure drops to the level that you have pre-set, the gear switch is triggered and your gear come down before its too late. Here is a picture of the prototype unit, look for an announcememt on my website soon.
The only problem with the testing so far is that my Super Hornet holds great air pressure..........but when testing on the ground and slowly bleeding out the air, it works flawless! Another feature of this unit is that it prevents your gear from colapsing if you turn your radio on with the gear switch in the "UP" position.......a feature that I found to be much in need around my demo team![:'(]
ORIGINAL: B58
I've got an idea I am going to try, and I really don't see why it won't work. On my Tams F-16 I am going to tee an airline into the down air line for the gear, with a check valve into the brake line. If I get an air leak in flight and can't extend the gear, I can hit the brakes on the other air system and gear will go down. If all is normal, the down air pressure will not be able to get into the brake system, so all will be as it should. All the full scale aircraft I have flown or been associated with always had an alternate gear extension, and this is so simple I am surprised I never tried it before. Any opinions or ideas? Thanks for the input. Bob